DW660 Lower Bearing Failure

Question about bearing failure on DW660

MPCNC running a DeWalt DW660, full speed (while I understand different spindle speeds and feed rates in different materials are variables to work with, I assume that the normal DW660 spindle speed also produces adequate, if not optimal, cooling air flow. You’ll see why in a few lines.) My usual feed rate is 480MM/Min. The DW660 is Off/On controlled through a solid-state relay by the motherboard/controller fan outputs - always full on or full off. I also have a manual by-pass for the relay.

I’ve made two mods to the DW660. Removing the “Quick Change” ‘knob’ (spindle/collet nut catcher). And, removing the power switch and rewiring it so that the power cord goes out the top of the housing where the “Emergency Off” button was.

Normal cutting depths are usually in the 1.0 +/- 0.5MM range, with occasional dips to 3MM or 4MM. Normal horizontal cut movement is also usually in the1.0 +/- 0.5MM range. Run time per cut is normally up to 3.5 hours, but has run as long as 5+ hours. (This is where my cooling air consideration comes in - I don’t want any over-heating in very long runs.)

I’m usually cutting dishes and bowls in various shaped up to 350MM x 350MM x 50MM. (Which might explain some of the long run times.) Materials being cut run from plywood, through soft woods (pine) and into medium density hardwoods. (I seldom dip into high density hardwoods, although I’m looking toward that for a couple of new projects floating around in my head.) Cutters range from 2MM flat nose up-cut end mills up to 1/2" round nose cove bits, and all bits are carbide.

In approx 2 years of work and play, I’ve run through 1 set of brushes,

Yesterday, after about 10 minutes of cutting a reasonably soft plastic, the DW660 seized and died quickly. Initial check suggested a seized bearing. A full take-apart found that the lower bearing assembly had seized completely. after looking at it and the parts diagram, it does not look like that bearing is going to be easily replaced.

Late yesterday, I ordered a replacement DW660.

My question is, has anybody else suffered any bearing failure issues with the DW660?

(Before you say it, yes, I’m long-winded and detailed in reports. It’s saved me a lot of grief when called as a witness in court, and tends to spill over into things like this… Sorry!)

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In routers, bearing failure can be common with long run times. Usually the manufacturer uses the least expensive version of the specced bearing, assuming normal intermittant operation. I have used Makita, and Makita clones routers on the MPCNC. Yep have worn out brushes, and yep, seized a bearing or two. When I have that problem of the seized bearing in any tool, I take the bearing to a bearing distributor and buy the best available, usually quite a few grades above “spec”. In the bearing world the grades are specified by ABEC rating, a system of bearing standards. ABEC 1 being the lowest and ABEC 12 being the highest. I also replace with sealed stainless sheilded, as it keeps dust and grit out of them better then the rubber sealed type. The ABEC rating is more common to see in the skateboard bearing world, but it is still the standard even if it is not listed
For example, I have a old Craftsman table saw I bought new in 1991, replaced the bearings 3 times with the manufacturer replacements, usually lasting 3-5 years. 8 years ago I replaced them with high spec double row sealed, run a higher HP motor now and quiet, and no bearing noise yet. Most power tools use the same bearing size in their motors that we use as the bearings running the trucks. As I always keep several hundred ABEC7’s around, I tend to use them.
From what I can tell on the parts lists, the bearing in the DW660 is a 6302-2RS. Usually a readily available type


Oh and that size I used quite a bit on printing press rollers. Think I have 50 or so in the cabinet. It is also a common bearing in the automotive world

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